172 



THE LIAS AMMONITES. 



Fig. 18. — Chiroteuthis Veranyi, Ferussac. 



Fig. 19. — Sepia vermiculata, d'Orh. 



filled with air and supported by columns, but not perforated by. a siphon (figs. 17 

 and 19). 



4. Family BELEMNiTiDiE, Owen, 1836. — An extinct family. Shell consisting of a pen, 

 terminating posteriorly in a chambered cone, sometimes inclosed in a sheath or guard. 



The air-cells of the phragmacone are connected 

 by a siphuncle close to the ventral side. The 

 animal possessed an ink-bag, which is often 

 found fossil in situ. The arms were provided 

 with recurved booklets, seen in situ in speci- 

 mens found in the Oxford Clay. The figures 

 20, 21, 22, on the margin are ideal restora- 

 tions of the animal of the Belemnites, and 

 drawn by the late Professor Alcide d'Orbigny, 

 who considered that the complete test of 

 Belemnites was composed of four parts inti- 

 mately united together. These parts are — 1st. 

 Anteriorly a horny spatuliform blade, enlarged 

 before and contracted behind. 2nd. A deep 

 cup or conical alveolus containing a series of 

 air-chambers. 3rd. An inferior siphon tra- 

 versing the whole series of chambers. 4th. A 

 calcareous sheath, more or less elongated, 

 covering and protecting the alveolus, and con- 

 stituting a true terminal rostrum, all which parts are shown in situ in the above figures 

 of the restored forms. 



5. Family SpiRULiDiE, d'Orhigny, 1837. — Body oblong, with small terminal fins; 



Fitts. 20 — 22. — Belemnites restored by d'Orbigny. 



